Madden Julian Oscillation (MJO)

Madden-Julian Oscillation (MJO) is a weather phenomenon that affects both the ocean and the atmosphere. It involves disturbances in wind, clouds, and air pressure, which travel eastward at a speed of 4-8 meters per second. This movement of the MJO has a significant impact on weather patterns worldwide. The ups and downs we experience in tropical weather on a weekly and monthly basis can be attributed to the influence of the Madden-Julian Oscillation.

What is Madden-Julian Oscillation (MJO)?

Madden-Julian Oscillation, or MJO, is a weather phenomenon that was identified in the 1970s. It’s like a globe-trotting weather pattern that affects conditions worldwide. MJO causes shifts in weather on a weekly and monthly basis, especially in tropical areas, notably over the Pacific Oceans and India. So, when you hear about changes in the weather, MJO might be the global traveler responsible for it!

It remains on the globe for an average of 30 to 60 days (sometimes it remains for 90 days).
The large cluster of clouds can range from 5000 to 10,000 Km in size and move towards the warm oceans from 60 65 degrees in the East to 150 180 degrees towards the East.

Madden-Julian Oscillation (MJO) is like a weather dance that happens in the Indian Ocean and travels across the globe. Picture it as a wave of moisture that brings lots of clouds and rain. It starts in the Indian Ocean and goes all the way to the International Date Line, creating a wet and cloudy path. But, there’s also a dry part that goes back to where it started. This whole back-and-forth movement is what we call oscillation.

The MJO does its dance for about 30 to 60 days, and it usually likes to show up during the winter season. While it’s a big player in the cyclone game, not all cyclones follow its lead – some just come from regular weather patterns, like the Rossby wave.

How does the MJO work?

Enhanced tropical rainfall initiates over the western Indian Ocean, extending eastward into the warm tropical Pacific. However, this pattern diminishes over the cooler eastern Pacific waters and reemerges over the Indian Ocean. The cycle involves a wet phase with heightened convection, succeeded by a dry phase marked by suppressed thunderstorm activity. Each cycle spans 30-60 days, comprising a total of 8 phases.

Phases of Madden-Julian Oscillation

Madden-Julian Oscillation (MJO) has two main phases. When the MJO is strong, it divides the Earth into two unequal parts known as the enhanced phase and the suppressed phase. In simple terms, during the enhanced phase, certain regions experience increased atmospheric activity, while in the suppressed phase, other areas have decreased activity. This pattern repeats as the MJO travels across the globe, impacting weather patterns in different regions.

Enhanced Rainfall Phase:

During the enhanced rainfall phase, winds converge at the Earth’s surface, causing air to rise into the atmosphere.
Aloft, the winds become more varied. This creates tension in the air movement, promoting increased condensation and leading to heightened rainfall.
Consequently, this phase is characterized by more rain, cloud cover, and even stormy weather.

Suppressed Rainfall Phase:

In the suppressed rainfall phase, winds at higher altitudes converge, compelling air to descend from the upper atmosphere.
This descending motion results in dry and warm atmospheric conditions, leading to the suppression of rainfall.
The suppressed phase is marked by dry weather, with more sunshine and a lack of significant rainfall.

How Does MJO Affect Indian Monsoon?

The Indian Ocean Dipole (IOD), El Nino and MJO are all oceanic and atmospheric phenomena, which affect weather on a large scale.
IOD only pertains to the Indian Ocean, but the other two affect weather on a global scale-up to the mid-latitudes.
IOD and El Nino remain over their respective positions, while MJO is a traversing phenomenon.
The journey of MJO goes through eight phases. When it is over the Indian Ocean during the Monsoon season, it brings good rainfall over the Indian subcontinent.
On the other hand, when it witnesses a longer cycle and stays over the Pacific Ocean, MJO brings bad news for the Indian Monsoon.
It is linked with enhanced and suppressed rainfall activity in the tropics and is very important for the Indian monsoonal rainfall.

How does the MJO affect weather around the world?

The Madden-Julian Oscillation (MJO) exerts various impacts on global weather patterns:

MJO and Cyclones: Monitored during the Atlantic hurricane season, the MJO creates conditions conducive to tropical cyclone activity.
Monsoon Impact: MJO’s enhanced rainfall phase triggers global monsoon onset, while the suppressed convection phase can delay monsoon seasons.
ENSO Connection: MJO influences the El Nino Southern Oscillation, affecting the speed and intensity of El Nino and La Nina development, particularly during neutral and weak ENSO years.
Sudden Stratospheric Warming: Evidence suggests MJO’s influence on the onset of Sudden Stratospheric Warming (SSW) events.